module sse import net import time import strings // This module implements the server side of `Server Sent Events`. // See https://developer.mozilla.org/en-US/docs/Web/API/Server-sent_events/Using_server-sent_events#event_stream_format // as well as https://html.spec.whatwg.org/multipage/server-sent-events.html#server-sent-events // for detailed description of the protocol, and a simple web browser client example. // // > Event stream format // > The event stream is a simple stream of text data which must be encoded using UTF-8. // > Messages in the event stream are separated by a pair of newline characters. // > A colon as the first character of a line is in essence a comment, and is ignored. // > Note: The comment line can be used to prevent connections from timing out; // > a server can send a comment periodically to keep the connection alive. // > // > Each message consists of one or more lines of text listing the fields for that message. // > Each field is represented by the field name, followed by a colon, followed by the text // > data for that field's value. [heap] pub struct SSEConnection { pub mut: headers map[string]string conn &net.TcpConn write_timeout time.Duration = 600 * time.second } pub struct SSEMessage { id string event string data string retry int } pub fn new_connection(conn &net.TcpConn) &SSEConnection { return &SSEConnection{ conn: conn } } // sse_start is used to send the start of a Server Side Event response. pub fn (mut sse SSEConnection) start() ? { sse.conn.set_write_timeout(sse.write_timeout) mut start_sb := strings.new_builder(512) start_sb.write_string('HTTP/1.1 200') start_sb.write_string('\r\nConnection: keep-alive') start_sb.write_string('\r\nCache-Control: no-cache') start_sb.write_string('\r\nContent-Type: text/event-stream') for k, v in sse.headers { start_sb.write_string('\r\n$k: $v') } start_sb.write_string('\r\n') sse.conn.write(start_sb.buf) or { return error('could not start sse response') } } // send_message sends a single message to the http client that listens for SSE. // It does not close the connection, so you can use it many times in a loop. pub fn (mut sse SSEConnection) send_message(message SSEMessage) ? { mut sb := strings.new_builder(512) if message.id != '' { sb.write_string('id: $message.id\n') } if message.event != '' { sb.write_string('event: $message.event\n') } if message.data != '' { sb.write_string('data: $message.data\n') } if message.retry != 0 { sb.write_string('retry: $message.retry\n') } sb.write_string('\n') sse.conn.write(sb.buf) ? }